July 3, 2007—Perched in Sydney Harbor, the concrete "shells" of the Sydney Opera House have become an icon for the country of Australia. Designed by Jørn Utzon in an architectural competition in 1957, the opera house opened for performances in 1973.

Last week the United Nations Educational, Scientific and Cultural Organization (UNESCO) named the opera house—along with 22 other sites—as universally significant locations by adding them to the World Heritage list.

The sites will join the list's 851 other properties, which are decided on by representatives from 21 countries that are part of the World Heritage Convention.

The Sydney Opera House's inclusion on the list is notable because it arrived without a single dissenting vote, said Roni Amelan, a UNESCO spokesperson.

There was a consensus that it was a truly outstanding, iconic building that was a defining moment in 20th-century architecture," Amelan told the Associated Press.

The Sydney Opera House is now the youngest site to be included on the World Heritage list.